150 Amp sub panel

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tbakelis

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Residential house with detached garage. 100 amp breaker in main feeding sub panel in garage. Sub panel in garage has a 150 amp main because there will be solar panels on roof of garage. In this situation I must use wires rated for 150 Amps, correct? 1/0 will do, right?

Thanks!
 
tbakelis said:
Residential house with detached garage. 100 amp breaker in main feeding sub panel in garage. Sub panel in garage has a 150 amp main because there will be solar panels on roof of garage. In this situation I must use wires rated for 150 Amps, correct? 1/0 will do, right?

Thanks!
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Your feeder breaker is 100 amps - the conductors only need to be sized for 100 amps. You could put 2000 amp switchboard at the garage end if you want and only feed it with 100 amp conductors if the calculated load is 100 amps or less.
 
kwired said:
Your feeder breaker is 100 amps - the conductors only need to be sized for 100 amps. You could put 2000 amp switchboard at the garage end if you want and only feed it with 100 amp conductors if the calculated load is 100 amps or less.
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kwired, isn't there something about having to oversize conductors for PV installs. I have never done one, but somehow I have a weird/ distant impression about these installs. This is only a learning question that I am asking.
 
jumper said:
kwired, isn't there something about having to oversize conductors for PV installs. I have never done one, but somehow I have a weird/ distant impression about these installs. This is only a learning question that I am asking.
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Sorry, somehow I missed the solar panel part.

I guess it would depend on how much power the panels can make for starters. I'm no expert in PV but sounds like anything over 100 amps on a 120/240 single phase system would be a pretty large PV setup.
 
This detached garage is built like a bomb shelter! So I think I am going to size the wires for 150 amps, since that is what the sub panel main breaker is..

1/0 does up to 170 amps correct? Could have I gone down to #1?
 
If the wires are connected to a 100 amp breaker at the house, there is no reason to use wire sized larger than 100 amps.
What is the rating of the bus in the garage panel? There may be 705.12(D) issues in this installation. (2011 code, if on the 2008 the rule would be in 690.64(B) )
 
don_resqcapt19 said:
If the wires are connected to a 100 amp breaker at the house, there is no reason to use wire sized larger than 100 amps.
What is the rating of the bus in the garage panel? There may be 705.12(D) issues in this installation. (2011 code, if on the 2008 the rule would be in 690.64(B) )
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You are right - I take back what I said and am going with my first response. If there is 100 amp breaker at the house there is no reason to run more than 100 amp conductors other than for voltage drop reasons.
 
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